Internet Protocol (IP) routers are ubiquitously employed to transmit or forward a data packet from one network to another network based on different criteria (e.g., IP destination address) and in accordance with certain protocols. For example, telephony routing over IP (TRIP) is a general routing protocol for advertising the reachability of telephony destinations, and for advertising attributes of the routes to those destinations, irrespective of the application (signaling) protocol in use. Basically, TRIP helps in exchange of routing information among various “TRIP” Speakers, also called location servers. A location server (LS) functions to exchange and store routing information for reachability of telephony prefixes. For instance, a TRIP LS can be queried to fetch a route for a particular telephony prefix and application protocol combination. Session protocols like H.323 and Session Initiation Protocol (SIP) can query a location server for routes to reach a particular telephony prefix.
TRIP introduces a concept of IP telephony administrative domains (ITADs), which typically covers all of the devices managed by a single organization. An ITAD consists of a set of resources consisting of gateways and at least one LS. By way of example, in a H.323 network, an ITAD could consist of a set of H.323 gateways interested in advertising prefixes via the TRIP speaker. Gateways interested in advertising the prefixes they terminate can “register” with the TRIP speaker. An example of an ITAD topology that includes session routers is described in U.S. Patent Publication No. 2002/0014282.
The Telephony Gateway Registration Protocol (TGREP) was developed several years ago for registration of telephony prefixes and to advertise routes to telephony destinations in a network. Basically, TGREP provides a registration mechanism that works with TRIP to dynamically exchange routes between location servers. The location servers, in turn, can propagate the routing information within the same, and other Internet telephony administrative domains. By way of example, TGREP is the protocol commonly used for gateways having an interface into the Public Switched Telephone Network (PSTN). TGREP is described in detail in the Internet Engineering Task Force (IETF) May 2002 document http://www.ietf.org/internet-drafts/draft-ietf-iptel-tgrep-07.txt.
A voice over IP (VoIP) network typically consists of one or more ITADs that are broken into geographic Points of Presence (POP), with each POP containing some number of gateways, and a proxy server element that fronts those gateways. The proxy server is responsible for managing access to the POP, and also for determining which of the gateways will receive any given call that arrives at the POP. In conjunction with the proxy server that routes the call signaling, there are two TRIP Speaker components, the “Ingress LS” and the “Egress LS”. The Ingress LS maintains TGREP peering relationship with one or more gateways. The routing information received from the gateways is further injected into the Egress LS, which in turn disseminates into the rest of the network on TRIP. The proxy server plus the two LS speaker components are often referred collectively as the proxy LS (pLS).
A call may traverse multiple ITADs before reaching its destination, e.g., either an IP phone or a PSTN phone set. Within each ITAD, one or more TRIP location servers may be present. When the call arrives at the ITAD, these LSs invoke their route selection function to decide which POP should take the call. At the selected POP, the pLS further selects a proper gateway to carry the call forward (e.g., to another POP, gateway, or another ITAD). In order for these LSs and pLSs to decide a proper route per call basis, attributes about all the usable routes must be collected and gathered for use by these LSs and pLSs as input to their route selection function.
Both TRIP and TGREP include a number of attributes that play a role in correct and efficient functioning of the protocol. For instance, the RoutedPath attribute in TRIP is used to specify the intermediate ITADs to be taken by the signaling protocol to reach the destination prefix. Similarly, TGREP defines several attributes to describe the routing status of a PSTN-gateway segment that the gateway gathers and reports to the pLS. These attributes include the TotalCircuitCapacity attribute that identifies the total number of PSTN circuits that are available on a route to complete calls. The TotalCircuitCapacity attribute is used in conjunction with the AvailableCircuits attribute, which identifies the number of PSTN circuits that are currently available on a route. Additionally, the CallSuccess attribute is an attribute used between a gateway and its peer LS to provide information about the number of normally terminated calls out of a total number of attempted calls.
One problem with the prior art is that protocols such as TGREP and TRIP only include attributes related to routing calls through the PSTN-gateway segment. That is, none of the existing routing protocols include attributes to reflect and accommodate the IP side routing capability for both PSTN gateway and IP-IP gateway cases.
Therefore, what is needed is a solution that improves the routing capability of an IP-IP gateway and which allows an LS (pLS) to have a complete picture of a gateway's routing capability of both IP-side(s) and/or PSTN-side so that the LSs (pLSs) can make better decisions in route selection.